1. Field of the Invention
The present invention relates to a method and apparatus for measuring the speed of a vehicle.
The flow of traffic is monitored and controlled and observance of speed limits for vehicles is watched on general roads and highways so as to ensure smooth driving and maintain safe speeds.
In constructing such a road monitoring system, equipment is necessary for determining the speed of a moving vehicle. The present invention relates to a technique for measuring the speed of a vehicle for this purpose.
2. Description of the Related Art
As will be explained later in detail with reference to the drawings, in the past, accurate measurement of the speed of a vehicle required the installation of an image pickup camera directly above the route of travel of the vehicle. That is, the image pickup camera was installed directly above the route of travel so that the image of the vehicle taken by the image pickup camera would move in only the vertical direction on a display screen, for example, a monitor screen. Toward this end, it was necessary to install mounting poles and an arm, provide an arm extending in the horizontal direction from the existing support of a traffic signal, use a pedestrian bridge, or devise other means.
If installing, mounting poles and an arm, however, there is the problem that the vehicular speed measuring system becomes considerably high in cost to construct the same. Further, there is the problem that during the construction work, the traffic has to be stopped.
If providing an arm extending in the horizontal direction from the existing support of a traffic signal, the arm attached to the support easily swings within a horizontal plane parallel to the road due to the wind pressure caused by wind or vehicles driving at a high speed and therefore there is the problem that accurate measurement of the speed.-of vehicles is not possible.
Further, if using a pedestrian bridge, the location of installation of vehicular speed measuring systems ends up being limited to places with pedestrian bridges and therefore there is the problem that the speed of vehicles cannot be measured at any desired location, which is inconvenient.
An object of the present invention is to provide a method and apparatus for measuring the speed of a vehicle which enable measurement of the speed of a vehicle with a high accuracy by an image pickup camera mounted to a single simple supporting pole installed at the side of a field.
That is, an object of the present invention is to enable measurement of the speed of a vehicle based on an image of the vehicle on a screen obtained by capturing the vehicle from a direction inclined relative to the route of travelxe2x80x94not from right above the route of travel of the vehicle as in the related art.
To attain the above object, the method of the present invention includes the steps of (S1) capturing a vehicle in motion by an image pickup unit mounted on a support provided at the side of a road, (S2) calculating an amount of movement in the vertical direction by an image of the vehicle captured by the image pickup unit on a display screen displaying the image, (S3) calculating an amount of movement in the horizontal direction by the image of the vehicle captured by the image pickup unit on the display screen displaying the image, (S4) converting the calculated amount of vertical movement and amount of horizontal movement based on information of the capture location of the image pickup unit in the real space of the vehicle and information of the attitude of the image pickup camera to an amount of vertical movement and amount of horizontal movement in that real space, and (S5) computing the speed of the vehicle from the amount of vertical movement and amount of horizontal movement in the real space of the vehicle and the movement time. Therefore, it becomes possible to accurately measure the speed of a vehicle being driven based on an image from an image pickup unit mounted on the top of a supporting pole installed at the side of a field.